In recent years, the information-oriented society has continued the rapid advance and the information recording capacity exceeding 200 Gbytes has been required per 2.5-inch magnetic disk in magnetic recording apparatuses represented by HDDs (hard disk drives). In order to satisfy such a requirement in the magnetic disk, it is necessary to realize an information recording density (areal recording density) exceeding 200 Gbits per square inch (200 Gbits/inch2). Since high recording resolution can be obtained in the perpendicular magnetic recording system comprising a perpendicular two-layer medium and a single-pole head, it has been studied and developed as the next-generation high-density recording system.
In a magnetic disk, an improvement in areal recording density is achieved by an improvement in track density and an improvement in linear density. As a method of improving the linear density of the two, there has conventionally been proposed a CGC (Coupled Granular and Continuous) medium having a granular layer (Granular layer) and a continuous film layer (Continuous layer) (see, e.g. Patent Document 1). In the CGC medium, three points, i.e. a reduction in magnetization transition region noise of a recording layer, an improvement in thermal stability of recorded signals, and easiness of recording, can be realized in a well-balanced manner and thus it is possible to properly improve the linear density.
In recent years, a DTR (discrete track) medium, a patterned (bit-patterned) medium, and the like have been proposed as a technique of improving the track density. In the DTR medium, the patterned medium, or the like, a nonmagnetic isolation region such as a groove is formed by, for example, a mechanical method between recording regions where magnetic signals are recorded, thereby magnetically isolating the recording regions from each other. This makes it possible to suppress the influence between the adjacent recording regions to thereby improve the track density. Further, conventionally, as a method of manufacturing a DTR medium, there is known a method of locally implementing Ag ions into a thin film having a predetermined composition (see, e.g. Patent Document 2). In this method, a portion where no Ag ions are implemented serves as a portion having a smaller coercive force.    Patent Document 1: U.S. Pat. No. 6,468,670B1 Specification    Patent Document 2: JP-A-2005-223177
First, the first invention will be described.